THE MEASUREMENT OF NITROUS-OXIDE EMISSIONS FROM SEWAGE SYSTEMS IN BELGIUM

To quantify the nitrous oxide emissions from waste water, an experimen tal measurement campaign has been set up; waste water was sampled at t he collector tubes entering sewage treatment plants and at the settlin g tanks in these plants. The gas phase developing in the static head s pace of the water samples was analysed; gas chromatography by means of electron capture detection was the analytical tool by which the nitro us oxide concentration in batch samples of gas was determined. The met hodological analysis was based on the concentration/time curves obtain ed. The formation of nitrous oxide from the waste water matrices is th e result of the microbiological denitrification of the organic substra te present; this could be deduced from the response of the nitrous oxi de signal to the addition of NaNO3. NH4NO3 and (NH4)2SO4 to the sample s. Application of the Lineweaver-Burk kinetic equation for enzyme-cata lysed reactions on our results, combined with the yearly mean nitrate concentration and the seasonal mean waste water temperature, enabled u s to deduce emission coefficients for the two types of waste water sam pled: raw waste water: (4.3 +/- 1.0) mug N2O/gss, settled waste water: (800 +/- 180) mug N2O/gss, where ''gss'' stands for ''gram suspended solids'', a water quality parameter continuously monitored in Belgium.